docs: def set_document_unit(self, unit):
          """Use specified unit for width and height of generated SVG file.
  
          See ``SVG_UNIT_*`` enumerated values for a list of available unit
          values that can be used here.
  
          This function can be called at any time before generating the SVG file.
  
          However to minimize the risk of ambiguities it's recommended to call it
          before any drawing operations have been performed on the given surface,
          to make it clearer what the unit used in the drawing operations is.
  
          The simplest way to do this is to call this function immediately after
          creating the SVG surface.
  
          Note if this function is never called, the default unit for SVG
          documents generated by cairo will be "pt". This is for historical
          reasons.
  
          :param unit: SVG unit.
  
          *New in cairo 1.16.*
  
          *New in cairocffi 0.9.*
  
          """
          cairo.cairo_svg_surface_set_document_unit(self._pointer, unit)
          self._check_status()